JPH06214045A - Fluid/flow sensor, and underground water investigating method using same - Google Patents

Abstract

PURPOSE:To measure a fluid/flow con-dimensionally and continuouly in point of time, and also investigate underground water level or the position or magnitude of underground water flow. CONSTITUTION:A fluidflow sensor 10 has a lengthy structure in which an optical fiber 12 and a heating wire 14 are covered with a heat resisting electric insulating material 16 and integrated. This fluid/flow sensor is set in the ground, a current is carried to the heating wire to generate heat, and the temperature distribution laid along the optical fiber is measured, whereby underground water level or flow is investigated. Further, the fluid/flow sensor is inserted into a boring in which underground water is present, the current is carried to the heating wire to generate heat while measuring the temperature distribution laid along the optical fiber, and the magnitude of the flow of underground water is investigated by the change on standing of temperature distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical fiber type fluid
The present invention relates to a flow sensor and a groundwater investigation method using the flow sensor. More specifically, by arranging a heating wire near the optical fiber, positively causing a disturbance such as a temperature rise on the object to be investigated, and detecting a temperature change due to the presence or flow of fluid, the reverse The present invention relates to a technology for investigating the existence (presence and absence and the existence position) of a fluid and the flow state. This fluid / flow sensor is particularly useful for investigation / monitoring of groundwater level and groundwater flow.

[0002]

2. Description of the Related Art Flow of groundwater means flow position, flow velocity, water level fluctuation, and the like. As a conventional technique for investigating and monitoring these, drilling a borehole in the ground,
There are a method of inserting a water level meter into the hole to measure the water level, and a method of introducing water-soluble salts into the hole to measure the electric conductivity. In addition, the suction force of water in the soil may be measured.

At present, an optical fiber type temperature distribution measuring system is a technology which is not related to groundwater investigation at present, but is related to the present invention. This is because when the optical fiber is irradiated with laser pulsed light, the temperature is measured by utilizing the fact that the intensity ratio of Stokes light and anti-Stokes light due to Raman scattering of backscattered light generated in the optical fiber is a function of temperature. The scattered light generation point is obtained by the delay time from the irradiation of the laser pulse light to the return to the incident end as the backscattered light. In this system, the optical fiber itself is a sensor, the temperature distribution on the line along the optical fiber can be measured, the length can be extended to about 10 km, and the position measurement accuracy is said to be about 1 m. This technique is used, for example, for measuring the geothermal temperature distribution as a survey of the natural environment.

[0004]

Each of the conventional groundwater investigation methods described above has its own characteristics, and is used properly according to the purpose of the investigation. However, when detecting and measuring the flow of groundwater from changes in the suction force in the soil, for example, a potentiometer is buried, but this is a point measurement, and if continuous measurement is performed linearly, a large number of There are limitations such as the need to embed sensors. When drilling a boring hole to detect the position where groundwater spouts from the hole wall into the hole, salt is poured into the hole, mixed, and the electrical conductivity is measured to make a large change. It is judged that there is a well in the part, but the measurement also has to be intermittent.

On the other hand, since the optical fiber type temperature distribution measuring system merely measures the temperature distribution (the temperature at each position in the longitudinal direction of the optical fiber), there is almost no temperature difference between the soil and water. In the ground, it cannot be used by itself for groundwater research.

An object of the present invention is to provide a fluid / flow sensor capable of continuous measurement in one dimension and time. Another object of the present invention is to provide a method capable of continuously measuring the groundwater level one-dimensionally and temporally, and also capable of investigating the position and magnitude of the groundwater flow.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a temperature distribution measuring type fluid / flow sensor in which an optical fiber and a heating wire arranged along the optical fiber are covered with a heat-resistant electrical insulating material and integrated. . The optical fiber and the heating wire may be arranged close to each other, and their shapes and combinations are arbitrary. Depending on the usage conditions (ambient environment), an electrically insulating material having corrosion resistance is used.

Further, according to the present invention, a heating wire is arranged along an optical fiber, and a fluid / flow sensor integrated with a heat-resistant electric insulating material is installed in the ground, and the heating wire is energized to generate heat. And measuring the temperature distribution along the optical fiber to investigate the water level or flow of groundwater. A fluid / flow sensor is inserted into a borehole where groundwater is present, and the heating wire is energized to generate heat while measuring the temperature distribution along the optical fiber, and the flow of groundwater is caused by the temporal change in the temperature distribution. There is also a method of investigating the size of.

[0009]

[Effect] Even if the object to be investigated has a substantially uniform temperature distribution, when a disturbance (temperature rise) is positively applied to the optical fiber, a factor that partially changes the temperature acts on it. The temperature distribution changes. The factors include extreme difference in physical properties (heat capacity) and fluid flow. Therefore, on the contrary, by measuring the temperature distribution after the disturbance (temperature rise) is applied, it is possible to investigate the difference in the physical properties and the fluid flow.

In the soil, for example, the temperature of each part is usually substantially constant regardless of the presence or absence of groundwater. When a fluid / flow sensor is installed in the soil and the heating wire is energized, the entire sensor heats up almost uniformly and the temperature rises above the surrounding temperature. However, since the heat capacity of soil (or air) is different from that of water, the degree of temperature rise is different between the part in contact with soil and the part in contact with water, and the temperature in the part in contact with water does not rise. Therefore, it is possible to detect the groundwater level by irradiating the optical fiber with laser pulsed light and measuring the temperature distribution while energizing the heating wire. When groundwater is flowing, the heat removal effect is further enhanced. The greater the flow, the smaller the temperature rising rate, and the lower the temperature at equilibrium. By tracking these phenomena, the location of the aquifer and the magnitude of groundwater flow can be detected.

[0011]

1 is an explanatory view showing an embodiment of a fluid / flow sensor according to the present invention. This fluid / flow sensor 10
Is a heat-resistant and corrosion-resistant electrical insulating material 1 for an optical fiber 12 and a heating wire 14 arranged closely along the optical fiber.
It is a long structure that is commonly covered with 6 and integrated.

FIG. 2A shows an example of a groundwater investigation method using the fluid / flow sensor. The fluid / flow sensor 10 is embedded in the ground 20 in the vertical direction and folded back at the bottom. A power source is connected to both ends of the heating wire to flow a constant current. A temperature distribution measuring device is connected to one end of the optical fiber. Here, it is assumed that the groundwater level L is at the illustrated position. The heating wire generates heat when energized, and the entire fluid / flow sensor 10 tries to rise to a substantially uniform temperature (however, a temperature much higher than the ambient temperature). At that time, the fluid / flow sensor 10 is in contact with the soil at the upper portion, but is in contact with the groundwater at the lower portion. Since the heat capacities of soil and water are significantly different and that of water is much larger, the temperature rise is different between the upper and lower portions of the fluid / flow sensor 10, and there is a difference in temperature distribution even in the equilibrium state. Fluid / flow sensor 10 in contact with water
The temperature is lower in the lower part of. That is, the temperature distribution shown in B of FIG. 2 can be detected. From this temperature distribution, it can be detected that groundwater exists below the low temperature level L.

FIG. 3A shows another example of the usage of the fluid / flow sensor 10, and B shows the temperature distribution at that time. Fluid in the boring hole 22 formed in the ground 20
The flow sensor 10 is inserted. The fluid / flow sensor 10 is folded back at the bottom of the boring hole 22. Similar to the above example, a power source is connected to both ends of the heating wire to flow a constant current, and a temperature distribution measuring device is connected to one end of the optical fiber. If there is an aquifer 24 in the ground and there is groundwater flow,
The heat removal effect in that portion is further enhanced. That is, as shown in FIG. 3B, heat is taken from the fluid / flow sensor 10 in the portion where there is groundwater flow, and the temperature drops. A constant temperature distribution is generated even in the equilibrium state, and by measuring it, the flow position of groundwater (position of aquifer) can be detected.

When the heating wire of the fluid / flow sensor starts to be energized, the temperature gradually rises, but the rate of temperature rise changes depending on the surrounding conditions. For example, when the temperature change is measured at the position of the aquifer, the temperature rising curve (relationship of temperature with time) is different as shown in FIG. From the case where the temperature rises quickly to the time when the temperature rises gradually (curve a, ...,
d) It varies. The greater the flow of groundwater, the higher the heat removal effect, and the slower the heating rate. That is, it can be seen that the flow becomes larger as the gradient becomes gentler, as shown by the curve a → curve d. Therefore, it is possible to determine the magnitude of groundwater flow by observing the temperature change after the energization of the heating wire is started. Further, when the energization is stopped, the temperature gradually drops, and the rate of temperature drop changes according to the surrounding conditions, so the magnitude of the flow can be known from the temperature drop curves (curves e, ..., H).

FIG. 5 shows another embodiment of the method of the present invention. In these examples, the fluid / flow sensor 10 is spirally wound and embedded in the ground 20 (A in FIG. 5),
It is inserted into a boring hole 22 formed in the ground 20. This improves the resolution. For example, about 30 in diameter
If it is configured to be wound at a pitch of 1 cm with a cm (circumferential length of 1 m), the groundwater level and the position of the aquifer can be specified with about 100 times accuracy compared to the case where they are arranged in a straight line. Although not shown in the drawings, in these cases, it is preferable that the fluid / flow sensor 10 be wound around and fixed to a cylindrical casing or the like because it can be easily inserted into a boring hole or the like.

The fluid / flow sensor according to the present invention is not limited to the above configuration. For example, in FIG.
As shown in FIG. 5, the optical fiber 32 and the heating wire 34 may be bent in the same manner at the intermediate portion and arranged close to each other, and may be commonly covered with the heat-resistant electric insulating material 36. By doing so, the workability of burying in the soil and inserting into the boring hole is further improved. Further, it becomes easy to connect the power source to both ends of the heating wire. Since the optical fiber irradiates the laser pulse light from one end to detect the backscattered light, only one optical fiber may be attached without being folded back.

The fluid / flow sensor according to the present invention can be used to detect the presence or flow of a liquid other than water.
It can also be used to detect gas flow (spouting, etc.).

[0018]

As described above, the present invention is a fluid / flow sensor having a long structure in which the optical fiber and the heating wire are closely arranged and covered with a heat-resistant electric insulating material. Therefore, the heating wire is energized to generate heat. By measuring the temperature distribution with the optical fiber, it is possible to continuously measure the existing position or flow state of the fluid one-dimensionally and temporally.

Especially when applied to groundwater investigation, it is only necessary to bury one fluid / flow sensor directly in the ground or insert it into the boring hole. Therefore, the sensor can be installed easily, the installation cost is low, and the groundwater Water level, aquifer position,
It is possible to continuously and accurately investigate the groundwater flow condition over the entire length of the sensor in the longitudinal direction.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a fluid / flow sensor according to the present invention.

FIG. 2 is an explanatory diagram showing an example of its usage status and temperature distribution.

FIG. 3 is an explanatory diagram showing another example of the usage status and temperature distribution.

FIG. 4 is an explanatory diagram of groundwater flow measurement by the method of the present invention.

FIG. 5 is an explanatory view showing another example of the investigation situation by the method of the present invention.

FIG. 6 is an explanatory view showing another embodiment of the fluid / flow sensor according to the present invention.

[Explanation of symbols]

 10 Fluid / Flow Sensor 12 Optical Fiber 14 Heating Wire 16 Electrical Insulation Material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seyuki Fujii 4-26, Kudankita, Chiyoda-ku, Tokyo Within Geological Co., Ltd. No. 6 Applied Geotechnical Co., Ltd.

Claims (3)

[Claims] 1. A fluid distribution / flow sensor of a temperature distribution measuring system, characterized in that an optical fiber and a heating wire arranged along the optical fiber are covered with a heat-resistant electric insulating material and integrated. 2. A heating / heating wire is arranged along an optical fiber, and a fluid / flow sensor integrated with a heat-resistant electrical insulating material is installed in the ground, and the heating wire is energized to generate heat. A groundwater investigation method characterized by investigating groundwater level or flow by measuring temperature distribution along an optical fiber. 3. A fluid / flow sensor in which a heating wire is arranged along an optical fiber, and which is covered with a heat-resistant electric insulating material and integrated, is inserted into a borehole in which groundwater exists, and the fluid / flow sensor is inserted along the optical fiber. A method for investigating groundwater, characterized in that the heating wire is energized to generate heat while measuring the temperature distribution, and the magnitude of groundwater flow is investigated by the temporal change of the temperature distribution.